In the production of polymers, such as elastomeric polymers by employing anionic or certain coordination catalysts systems, it is often desirable to synthesize polymers that have a narrow molecular weight distribution. When employing these reaction techniques, the molecular weight is directly proportional to the residence time of the reactants within the reactor (i.e., reaction time). As a result, it is often desirable to synthesize these polymers in a batch system because the residence time can be easily controlled. In other words, the reaction time for any of the reactants within a batch system can be controlled such that the individual reactants can each have a nearly identical or uniform reaction time.
Continuous systems have historically not been preferred for the production of polymers having narrow molecular weight distribution because the residence time of any of the given reactants within a continuous system cannot be easily controlled or regulated. Within a typical continuous plug flow system, parabolic velocity occurs within reactors of sufficient diameter resulting in a non-uniform range of residence times for the various reactants or products. As a result of this non-uniform residence time, a broad range of molecular weights results. This could possibly be alleviated by operating the system at very high fluid velocities, but this would result in very high system pressure drops when attempting to produce polymers having molecular weights of commercial interest.
Within a continuously stirred tank reactor (CSTR), the mixing of ingredients, which results in backmixing, likewise results in a non-uniform residence time among the various reactants or products. As a result of this non-uniform residence time, polymers having various molecular weight distributions are produced.
Because it would be advantageous to continuously polymerize polymers having a narrow molecular weight distribution, there is a need to develop a process or reactor that will allow for the continuous polymerization of monomer and achieve polymers having a narrow molecular weight distribution.